Method of generating fingerprint image and fingerprint sensor

ABSTRACT

A method of generating a finger image includes determining a quantity of electric charge to be removed from each of a plurality of detection circuits connected to a fingerprint sensor, based on an amplifier characteristic of each of the plurality of detection circuits; obtaining a second electrical quantity by removing the quantity of electric charge from a first electrical quantity that is input to each of the plurality of detection circuits; integrating the second electrical quantity to obtain an integrated value; and generating the fingerprint image based on comparison between the integrated value of the second electrical quantity and a predetermined threshold value.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.10-2019-0133271, filed on Oct. 24, 2019 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND 1. Field

Apparatuses and methods consistent with example embodiments relate togenerating a fingerprint image and a fingerprint sensor.

2. Description of Related Art

Demand for personal authentication using unique characteristics of aperson such as fingerprints, voice, face, hand, or iris has graduallyexpanded. A personal authentication function is mainly used for bankingdevices, access control devices, mobile devices, or laptop computers.Recently, as mobile phones such as smartphones have been widelydistributed, a fingerprint recognition apparatus for personalauthentication is employed to protect much security information storedin a smartphone.

SUMMARY

Example embodiments provide a method of generating a fingerprint image,fingerprint sensor, and a computer-readable recording medium havingrecorded thereon a program for executing the method. The technicalproblem to be solved is not limited to the above technical problems, andother technical problems may exist.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to an aspect of an example embodiment, there is provided amethod of generating a fingerprint image, including: determining aquantity of electric charge to be removed from each of a plurality ofdetection circuits connected to a fingerprint sensor, based on anamplifier characteristic of each of the plurality of detection circuits;obtaining a second electrical quantity by removing the quantity ofelectric charge from a first electrical quantity that is input to eachof the plurality of detection circuits; integrating the secondelectrical quantity to obtain an integrated value; and generating thefingerprint image based on comparison between the integrated value ofthe second electrical quantity and a predetermined threshold value.

Each of the plurality of detection circuits may include a currentsource, and a switch configured to connect the current source to theplurality of detection circuits according to a control signal. Thedetermining the quantity of electric charge may include determining thequantity of electric charge based on an amount of a current generatedfrom the current source included in each of the plurality of detectioncircuits and a turn-on time of the switch.

The predetermined threshold value may correspond to an input offsetvoltage of an amplifier included in each of the plurality of detectioncircuits.

The method may further include: determining the input offset voltage ofthe amplifier determined based on an output value of an analog-digitalconverter (ADC) included in each of the plurality of detection circuits.

The determining of the quantity of electric charge may includedetermining the quantity of electric charge such that a first componentof the first electrical quantity is not less than the input offsetvoltage of the amplifier.

The method may further include: determining a maximum turn-on time ofthe switch during which a first component of the first electricalquantity is not less than an input offset voltage of an amplifierincluded in each of the plurality of detection circuits, by increasingthe turn-on time of the switch while the amount of the current generatedfrom the current source is fixed; and determining a maximum currentamount of the current source at which the first component is not lessthan the input offset voltage of the amplifier, by adjusting the turn-ontime of the switch and the amount of the current generated from thecurrent source, wherein the obtaining the second electrical quantity mayinclude obtaining the second electrical quantity by determining thequantity of electric charge based on the maximum turn-on time and themaximum current amount, and by removing the determined quantity ofelectric charge from the first electrical quantity.

The method may further include: determining a maximum current amount ofthe current source at which a first component of the first electricalquantity is not less than an input offset voltage of an amplifierincluded in each of the plurality of detection circuits, by increasingthe amount of the current generated from the current source, when theturn-on time of the switch is fixed; and determining a maximum turn-ontime of the switch during which the first component is not less than theinput offset voltage, by adjusting the turn-on time of the switch andthe amount of the current generated from the current source, wherein theobtaining the second electrical quantity may include obtaining thesecond electrical quantity by determining the quantity of electriccharge based on the maximum current amount and the maximum turn-on time,and by removing the quantity of electric charge from the firstelectrical quantity.

The method may further include: based on the integrated value beinggreater than or equal to the predetermined threshold value, repeating atleast once the determining the quantity of electric charge and theintegrating the second electrical quantity.

The predetermined threshold value may represent a signal-to-noise ratioof each of the plurality of detection circuits.

According to an aspect of another example embodiment, there is provideda non-transitory computer-readable recording medium having recordedthereon a program for executing the method of generating the fingerprintimage.

According to an aspect of another example embodiment, there is providedan apparatus including: a fingerprint sensor including a plurality ofdrive electrodes and a plurality of detection electrodes; a plurality ofdetection circuits connected to the fingerprint sensor; and at least oneprocessor configured to: determine a quantity of electric charge to beremoved from each of the plurality of detection circuits, based on anamplifier characteristic of each of the plurality of detection circuits;obtain a second electrical quantity by removing the quantity of electriccharge from a first electrical quantity that is input to each of theplurality of detection circuits; integrate the second electricalquantity to obtain an integrated value; and generate a fingerprint imagebased on comparison between the integrated value of the secondelectrical quantity and a predetermined threshold value.

Each of the plurality of detection circuits may include a currentsource, and a switch configured to connect the current source to theplurality of detection circuits according to a control signal. The atleast one processor may be further configured to determine the quantityof electric charge based on an amount of a current generated from thecurrent source included in each of the detection circuits and an turn-ontime of the switch.

Each of the plurality of detection circuits may include an amplifier.The predetermined threshold value may correspond to an input offsetvoltage of the amplifier included in each of the plurality of detectioncircuits.

The at least one processor may be further configured to determine theinput offset voltage of the amplifier based on an output value of ananalog-digital converter (ADC) included in each of the plurality ofdetection circuits.

The at least one processor may be further configured to determine thequantity of electric charge such that a first component of the firstelectrical quantity is not less than the input offset voltage of theamplifier.

The at least one processor may be further configured to: determine amaximum turn-on time during which a first component of the firstelectrical quantity is not less than an input offset voltage of anamplifier included in each of the plurality of detection circuits, byincreasing the turn-on time of the switch while the amount of thecurrent generated from the current source is fixed; determine a maximumcurrent amount of the current source at which the first component is notless than the input offset voltage of the amplifier, by adjusting theturn-on time and the amount of the current generated from the currentsource, and obtain the second electrical quantity by determining thequantity of electric charge based on the maximum turn-on time and themaximum current amount and by removing the determined quantity ofelectric charge from the first electrical quantity.

The at least one processor may be further configured to: determine amaximum current amount of the current source at which a first componentof the first electrical quantity is not less than an input offsetvoltage of an amplifier included in each of the plurality of detectioncircuits, by increasing the amount of the current generated from thecurrent source, when the turn-on time of the switch is fixed; determinea maximum turn-on time of the switch during which the first component isnot less than the input offset voltage, by adjusting the turn-on time ofthe switch and the amount of the current generated from the currentsource, and obtain the second electrical quantity by determining thequantity of electric charge based on the maximum current amount and themaximum turn-on time, and by removing the quantity of electric chargefrom the first electrical quantity.

The at least one processor may be further configured to, based on theintegrated value being greater than or equal to the predeterminedthreshold value, repeat at least once an operation of determining thequantity of electric charge and an operation of integrating the secondelectrical quantity.

The predetermined threshold value may represent a signal-to-noise ratioof each of the plurality of detection circuits.

According to an aspect of another example embodiment, there is providedan electronic apparatus including: a fingerprint sensor comprising aplurality of drive electrodes and a plurality of detection electrodes; aplurality of detection circuits configured to receive a first electricalquantity from the plurality of detection electrodes of the fingerprintsensor, respectively, the plurality of detection circuits including ananalog-digital converter (ADC), a current source, and a switchconfigured to connect the current source to the ADC; and at least oneprocessor configured to: determine a candidate quantity of electriccharge to be removed from each of the plurality of detection circuits,based on an output voltage of the ADC; integrate a second electricalquantity that is obtained by removing the candidate quantity of electriccharge from the first electrical quantity, a first number of times untilthe first electrical quantity becomes less than a predeterminedthreshold value; and determine a final quantity of electric charge to beremoved from each of the plurality of detection circuits, based on anintegrated value of the second electrical quantity that is obtained byintegrating the second electrical quantity a second number time that isone less than the first number of times; and generate a fingerprintimage by removing the final quantity of electric charge from theplurality of detection circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain example embodiments, with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates an example of an apparatus for generating afingerprint image according to an example embodiment;

FIG. 2 illustrates a concept of a mutual capacitance corresponding toeach of nodes of a sensor according to an example embodiment;

FIG. 3 illustrates an example of a detection circuit included in areceiving circuit according to an example embodiment;

FIG. 4 is a flowchart of an example of a method of generating afingerprint image according to an example embodiment;

FIG. 5 is a flowchart of an example of determining, by a processor, aquantity of electric charge according to an example embodiment;

FIG. 6 illustrates an example of determining, by a processor, a finalquantity of electric charge according to an example embodiment;

FIG. 7 is a flowchart of an example of setting, by a processor, acandidate quantity of electric charge according to an exampleembodiment;

FIG. 8 illustrates in detail the method described in the flowchart ofFIG. 7 according to an example embodiment;

FIG. 9 is a flowchart of another example of setting, by a processor, acandidate quantity of electric charge according to an exampleembodiment;

FIG. 10 illustrates another example of a detection circuit included in areceiving circuit according to an example embodiment; and

FIG. 11 illustrates a fingerprint image according to an exampleembodiment and fingerprint images according to comparative examples.

DETAILED DESCRIPTION

The terms used in the present disclosure have been selected fromcurrently widely used general terms in consideration of the functions inthe present disclosure. However, the terms may vary according to theintention of one of ordinary skill in the art, case precedents, and theadvent of new technologies. Furthermore, for special cases, meanings ofthe terms selected by the applicant are described in detail in thedescription section. Accordingly, the terms used in the presentdisclosure are defined based on their meanings in relation to thecontents discussed throughout the specification, not by their simplemeanings.

When a part may “include” a certain constituent element, unlessspecified otherwise, it may not be construed to exclude anotherconstituent element but may be construed to further include otherconstituent elements. Furthermore, the terms such as “˜portion”,“˜unit”, and “˜module” stated in the specification may signify a unit toprocess at least one function or operation and the unit may be embodiedby hardware, software, or a combination of hardware and software.

Expressions such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list. For example, the expression, “at leastone of a, b, and c,” should be understood as including only a, only b,only c, both a and b, both a and c, both b and c, all of a, b, and c, orany variations of the aforementioned examples.

Hereinafter, the present disclosure will be described in detail byexplaining preferred embodiments of the disclosure with reference to theattached drawings. However, the present disclosure is not limitedthereto and it will be understood that various changes in form anddetails may be made therein.

In the following description, example embodiments are described indetail with reference to the drawings.

FIG. 1 illustrates an example of an apparatus 100 for generating afingerprint image according to an example embodiment. The apparatus 100may be also referred to as a fingerprint reader or a fingerprintscanner.

Referring to FIG. 1, the apparatus 100 may include a sensor 110, anelectronic circuit 120, a processor 123, a memory 124, and a display125. Furthermore, the electronic circuit 120 may include a transmittingcircuit 121 and a receiving circuit 122. Although FIG. 1 illustratesonly constituent elements related to the apparatus 100, it will beunderstood by those of ordinary skill in the art that othergeneral-purpose constituent elements may be further included.

The processor 123 may be embodied by an array of a plurality of logicgates, or a combination of a general-purpose microprocessor and a memorystoring a program that is executable on the microprocessor. Furthermore,it will be understood by those of ordinary skill in the art that theprocessor 123 may be embodied in hardware of a different form.

The sensor 110 may include a plurality of drive electrodes Tx and aplurality of detection electrodes Rx arranged in a directionintersecting the drive electrodes Tx. Although FIG. 1 illustrates thatthe number of the drive electrodes Tx and the number of the detectionelectrodes Rx are ten, respectively, the disclosure is not limitedthereto.

The transmitting circuit 121 may apply drive signals to the driveelectrodes Tx, and the receiving circuit 122 may measure electricalsignals from the detection electrodes Rx.

The drive electrodes Tx and the detection electrodes Rx of the sensor110 may be arranged in directions intersecting each other. Although FIG.1 exemplarily illustrates that the drive electrodes Tx and the detectionelectrodes Rx are arranged to be orthogonal to each other, thedisclosure is not limited thereto. In other words, an angle between thedirection in which the drive electrodes Tx are arranged and thedirection in which the detection electrodes Rx are arranged may not be90°.

When a user's finger approaches the sensor 110, mutual capacitancebetween each of the drive electrodes Tx and the detection electrodes Rxof the sensor 110 may vary. For example, the mutual capacitance at eachnode where the drive electrodes Tx and the detection electrodes Rxintersect each other in the sensor 110 may vary according to afingerprint pattern of a user. As the interval between the driveelectrodes Tx and the interval between the detection electrodes Rxdecrease, the resolution of a fingerprint sensor may increase. Apassivation layer for protecting the drive electrodes Tx and thedetection electrodes Rx may be further included in the sensor 110.

For example, the drive electrodes Tx and the detection electrodes Rx mayinclude line electrodes. Furthermore, each of the drive electrodes Txmay further include certain patterns provided between nodes where thedrive electrodes Tx and the detection electrodes Rx intersect eachother. The above-described pattern may have various shapes such as apolygon or a circle. Likewise, each of the detection electrodes Rx mayfurther include certain patterns provided between the above-describednodes.

The transmitting circuit 121 may apply drive signals to the driveelectrodes Tx. For example, the transmitting circuit 121 may apply avoltage pulse to each of the drive electrodes Tx. The receiving circuit122 may measure electrical signals from the detection electrodes Rx. Asan example, the receiving circuit 122 may measure a current flowing ineach of the detection electrodes Rx. As another example, the receivingcircuit 122 may measure an electric potential of each of the detectionelectrodes Rx.

The processor 123 generally control the operations of the transmittingcircuit 121 and the receiving circuit 122 included in the apparatus 100.For example, the processor 123 may control the amplitude and applicationduration of the voltage pulse applied by the transmitting circuit 121 toeach of the drive electrodes Tx. Furthermore, the processor 123 maycontrol the transmitting circuit 121 such that a voltage pulse may beselectively applied to some of the drive electrodes Tx.

The processor 123 may generate and process data related to a fingerprintusing the current or electric potential received by the receivingcircuit 122. For example, the processor 123 may generate datacorresponding to a fingerprint image using the current or electricpotential received by the receiving circuit 122, and generate afingerprint image using pixel values included in the data.

FIG. 2 illustrates a concept of a mutual capacitance corresponding toeach of nodes of the sensor 110 according to an example embodiment.

Referring to FIG. 2, the mutual capacitance between the drive electrodesTx and the detection electrodes Rx may correspond to the nodes where thedrive electrodes Tx and the detection electrodes Rx intersect eachother.

For example, mutual capacitance C11 between a first drive electrode Tx1and a first detection electrode Rx1 may be detected from a node N11where the first drive electrode Tx1 and the first detection electrodeRx1 intersect each other. Likewise, mutual capacitance Cmn between anm-th drive electrode Txm and an n-th detection electrode Rxn may bedetected from a node Nmn where the m-th drive electrode Txm and the n-thdetection electrode Rxn intersect each other. Here, “m” and “n” denotenatural numbers. In the following description, the mutual capacitance atthe node Nmn means a mutual capacitance between the m-th drive electrodeTxm and the n-th detection electrode Rxn.

A plurality of channels of the sensor 110 may be defined by the driveelectrodes Tx and the detection electrodes Rx. For example, theplurality of channels may respectively correspond to a plurality ofnodes formed at the intersections of the drive electrodes Tx and thedetection electrodes Rx. For example, a channel CH11 may correspond tothe node N11.

For example, to measure the mutual capacitance at each of a plurality ofnodes, the transmitting circuit 121 may sequentially apply differentdrive signals to the respective drive electrodes Tx. Furthermore, thereceiving circuit 122 may measure an individual electrical signal fromeach of the detection electrodes Rx. For example, when the mutualcapacitance C11 is to be measured, a drive signal may be applied to thefirst drive electrode Tx1, and the electrical signal from the firstdetection electrode Rx1 may be measured. Likewise, when the mutualcapacitance Cmn is to be measured, a drive signal may be applied to them-th drive electrode Txm, and the electrical signal from the n-thdetection electrode Rxn may be measured.

The receiving circuit 122 may include detection circuits respectivelyconnected to the detection electrodes Rx. An example detection circuitis described below with reference to FIG. 3.

FIG. 3 illustrates an example of a detection circuit 300 included in thereceiving circuit 122 according to an example embodiment.

Referring to FIG. 3, the detection circuit 300 may include a first part310 and a second part 320. Although only constituent elements related tothe detection circuit 300 of FIG. 3 are illustrated, it will beunderstood by those of ordinary skill in the art that othergeneral-purpose constituent elements may be further included.

The first part 310 may process an input electrical signal received fromone of the detection electrodes Rx, and may include at least oneamplifier AMP and a feedback capacitor Cf. The at least one amplifierAMP may be implemented as an operational amplifier. The input electricalsignal received from the detection electrode Rx may be expressed as anelectrical quantity indicating an object detected by the sensor 110. Inthis case, the electrical quantity may be used to describe a certainelectrical property, parameter, or attribute that may be quantified by acertain measurement. For example, the electrical quantity may include anelectric charge, a current, a voltage, an impedance, a capacitance(mutual capacitance), or a resistance. When an object detected by thesensor 110 is assumed to be a fingerprint, an electrical quantity outputfrom the detection electrode Rx may be expressed as a voltage differencebetween a voltage corresponding to a ridge of a fingerprint and avoltage corresponding to a valley of the fingerprint, or a capacitancedifference between the ridge and the valley, that is, a capacitancedifference ΔCm between the mutual capacitance corresponding to the ridgeand the mutual capacitance corresponding to the valley.

The second part 320 may generate a quantity of electric charge to beremoved from the electrical quantity to be input to the first part 310,and may include a current source Idc and a switch SW. The electriccharge Q is generated by current I supplied from the current source Idand a switch connection time (or a switch turned-on time) t during whichthe switch SW is turned on. The quantity of electric charge Q may beequal to a multiplication of the current I and the switch connectiontime (i.e., Q=I×t). The charge provided from the detection circuit 300may be reduced as much as the quantity of charge generated by the secondpart 320. In other words, the quantity of electric charge generated bythe second part 320 is removed from the electrical quantity input to thefirst part 310, and a result of the removal is output to an outputterminal Vout via the first part 310. Accordingly, as a closed time ofthe switch SW extends, the quantity of electric charge generated fromthe second part 320 may increase and the total quantity of chargegenerated from the detection circuit 300 may decrease. Furthermore, asthe amount of the current generated by the current source Idc increases,the electrical quantity removed from the electrical quantity generatedby the first part 310 increases.

An input terminal Vin of the detection circuit 300 may be connected toany one of the detection electrodes Rx included in the sensor 110. Inother words, assuming that the sensor 110 includes n-number of thedetection electrodes Rx, the receiving circuit 122 may include n-numberof the detection circuits 300.

As described above with reference to FIG. 1, the passivation layer maybe deposited on the sensor 110. In general, in a system adopting acapacitive sensor, as the thickness of a sensor increases, it may bemore difficult to obtain a quality image. When a capacitive sensorsystem detects a user's fingerprint, the mutual capacitance ΔCmcorresponding to a capacitance difference between the ridge and thevalley of a fingerprint is inversely proportional to the square of thethickness of the passivation. Accordingly, when the thickness of thepassivation is greater than or equal to a certain condition, it may bedifficult to detect the mutual capacitance ΔCm corresponding to thecapacitance difference between the ridge and the valley of afingerprint.

The quality of a fingerprint image may be proportional to the amount ofthe mutual capacitance ΔCm corresponding to the capacitance differencebetween the ridge and the valley of a fingerprint. Accordingly, as theamount of the mutual capacitance ΔCm corresponding to the capacitancedifference between the ridge and the valley of a fingerprint decreases,the quality of a fingerprint image is lowered.

Accordingly, in general, the system adopting a capacitive sensoraccumulates the mutual capacitance ΔCm corresponding to the capacitancedifference between the ridge and the valley of a fingerprint byintegrating several to several hundred times a signal input to the inputterminal Vin of FIG. 3, that is, a signal from the detection electrodeRx.

As a maximum voltage Vdd to be usable by the first part 310 exists, theavailable number of the above-described integrals may be limited. Inother words, the above-described integral may be repeatedly performeduntil an output Vout according to the quantity of electric chargeobtained through the integral becomes greater than or equal to themaximum voltage Vdd to be usable by the first part 310, or until thequantity of electric charge obtained through the integral becomes equalto the capacity of the feedback capacity Cf of the first part 310. Ingeneral, as the number of integrals increase, a signal-to-noise ratio ofa signal output from the output terminal Vout is improved. However, asdescribed above, as the number of integrals is limited due to themaximum voltage Vdd, unnecessary quantity of electric charge may beremoved as much as possible from the quantity of electric charge or themutual capacitance ΔCm obtained through the integral.

The detection circuit 300 according to an example embodiment may includethe second part 320, and when the switch SW of the second part 320 isclosed, electric charges from the current source Idc to the first part310 are removed so that the electric charges input to the first part 310are reduced. Accordingly, even when the integrals are repeatedlyperformed by the first part 310, the quantity of electric chargeobtained through the integral may not exceed an integral limit value.Accordingly, the number of integrals to be performed increases, whichleads to the improvement of the quality of a fingerprint image. In thefollowing description, for convenience of explanation, a decrease in theelectric charges input to the first part 310 is expressed to be aremoval of the electric charges input to the first part 310.

In particular, the second part 320 of the detection circuit 300 isindividually connected to the first part 310. In other words, while asingle second part is not connected to a plurality of first parts, eachsecond part 320 is connected to each first part 310. Accordingly, evenwhen the specifications and/or parameters of the detection circuits 300connected to the sensor 110 are different from each other, an optimalquantity of electric charge may be removed for each of the detectioncircuits 300.

An example of generating an image of an object detected by the sensor110 as the apparatus 100 removes an optimal quantity of electric chargefor each detection circuit 300 and integrating the quantity of electriccharge where unnecessary electric charges are removed is described withreference to FIGS. 4 to 10.

FIG. 4 is a flowchart of an example of a method of generating afingerprint image according to an example embodiment.

Referring to FIG. 4, a method of generating a fingerprint image mayinclude operations that are time-serially processed by the apparatus 10,the sensor 110, and the electronic circuit 120 illustrated in FIGS. 1 to3. Accordingly, it may be seen that the descriptions presented aboveregarding the apparatus 10, the sensor 110, and the electronic circuit120 illustrated in FIGS. 1 to 3, even though the descriptions areomitted below, are applied to the image generating method of FIG. 4.

In operation 410, the processor 123 may determine a quantity of electriccharge detected by each of the detection circuits 300 based on thespecifications and/or parameters of the detection circuits 300 includedin the electronic circuit 120. For example, the specifications andparameters of the detection circuits 300 may include a phase margin, again margin, a differential voltage gain, an input capacitance, and aninput offset voltage of an amplifier of each of the detection circuits300, but are not limited thereto.

For example, the processor 123 may determine a quantity of electriccharge based on an offset of the detection circuit 300 (e.g., an inputoffset voltage of the amplifier of the detection circuit 300). Theoffset may be determined by an output value of an analog-digitalconverter (ADC) at the rear end of the detection circuit 300. Forexample, the processor 123 may determine a quantity of electric chargesuch that a first component of a first electrical quantity input to thedetection circuit 300 is not less than the offset of the detectioncircuit 300. For example, assuming that the sensor 110 is a sensor fordetecting a fingerprint, the first component may be a voltagecorresponding to the ridge of a fingerprint, but the disclosure is notlimited thereto.

The processor 123 adjusts the amount of the current generated in thecurrent source Idc included in the detection circuit 300 and anoperation time of the switch SW connected to the current source Idc, soas to correspond to the determined quantity of electric charge. Forexample, the processor 123 calculates a quantity of electric charge byadjusting the amount of the current generated in the current source Idcand the operation time of the switch SW. For example, an electric chargequantity Q may be determined by a multiplication of the current amount Iand a time T during which the current flows. Accordingly, the processor123 may calculate the quantity of electric charge based on the amount ofthe current generated in the current source Idc and the operation timeof the switch SW.

The operation time of the switch SW means a time during which the switchSW is closed and becomes a conductive state. For example, referring tothe detection circuit 300 of FIG. 3, a current to be removed from thefirst part 310 is determined based on the time during which the switchSW is closed.

An example in which the processor 123 determines the quantity ofelectric charge corresponding to the detection circuit 300 and theamount of the current of the current source Idc and the operation timeof the switch SW are adjusted to correspond to the determined quantityof electric charge is described below with reference to FIGS. 5 to 9.

In operation 420, the processor 123 integrates a second electricalquantity obtained by removing the quantity of electric charge determinedin operation 410 from the first electrical quantity input to each of thedetection circuits 300.

For example, when the sensor 110 is a sensor for detecting afingerprint, the first electrical quantity may be an a differencebetween a voltage corresponding to a ridge of a fingerprint and avoltage corresponding to a valley of the fingerprint, or a capacitancedifference between the ridge and the valley, that is, a difference ΔCmbetween the mutual capacitance corresponding to the ridge and the mutualcapacitance corresponding to the valley.

The processor 123 removes the quantity of electric charge determined inoperation 410 from the first electrical quantity. The processor 123integrates a second electrical quantity obtained by removing somequantity of electric charge from the first electrical quantity.Accordingly, the amount of the mutual capacitance ΔCm corresponding tothe difference between the ridge and the valley of a fingerprint mayincrease.

As described above with reference to FIG. 3, as a limit value ofintegral exits, the available number of the above-described integralsmay be restricted. However, as the processor 123 integrates the secondelectrical quantity, the available number of integrals increases.Accordingly, the quality of the image generated by the processor 123 isimproved, as least because the mutual capacitance at each node of thesensor 110 is removed by an amount adjusted for each of the detectioncircuits 300 according to the specification/parameter (e.g., an inputoffset voltage of an amplifier of each of the detection circuits 300).

In operation 430, the processor 123 generates an image corresponding tothe detection of the sensor 110 connected to the electronic circuit 120according to whether a result of the integral of operation 420 satisfiesa certain condition.

For example, the processor 123 may generate the image corresponding tothe detection of the sensor 110 only when the result of the integral ofoperation 420 satisfies a certain condition. The certain condition maybe a certain signal-to-noise ratio, for example, 10 dB or more. However,the certain condition is not limited to the above description.

When the result of the integral of operation 420 does not satisfy thecertain condition, the processor 123 may repeat operation 410 andoperation 420 at least once. For example, when the result of theintegral does not satisfy a certain signal-to-noise ratio, the processor123 determines again the quantity of electric charge based on a thirdelectrical quantity obtained by integrating the second electricalquantity. In other words, the processor 123 determines again thequantity of electric charge such that a first component of the thirdelectrical quantity is not less than the offset of the detection circuit300.

The processor 123 readjusts the amount of the current generated in thecurrent source Idc included in the detection circuit 300 and theoperation time of the switch SW connected to the current source Idc, tocorrespond to the redetermined quantity of electric charge.

The processor 123 reintegrates a fourth electrical quantity obtained byremoving the redetermined quantity of electric charge from the thirdelectrical quantity. The processor 123 generates the image correspondingto the detection of the sensor 110 only when the reintegrated resultsatisfies a certain condition. When the reintegrated result does notsatisfy the certain condition, the above-described processes ofdetermining the quantity of electric charge, removing the quantity ofelectric charge, and integrating the electrical quantity are repeated.

The processor 123 may generate a high quality image representing anobject detected by the sensor 110 through the above-described processes.

FIG. 5 is a flowchart of an example of determining, by a processor, aquantity of electric charge according to an example embodiment.

In operation 510, the processor 123 checks an offset of each of thedetection circuits 300. For example, the processor 123 may determine, tobe an offset, an output value of the ADC included in the detectioncircuit 300 when the integral of electrical quantity is not performed.

In operation 520, the processor 123 checks a first component among therespective inputs of the detection circuits 300. For example, theprocessor 123 may check a first component from the electrical quantityinput to the detection circuit 300. When the sensor 110 is a sensor fordetecting a fingerprint, the first component may be a voltagecorresponding to the ridge of a fingerprint, the disclosure is notlimited thereto.

In operation 530, the processor 123 sets a candidate quantity ofelectric charge. For example, the processor 123 may set the candidatequantity of electric charge by adjusting parameters of parameters of thecurrent source Idc and the switch SW of the second part 320 of thedetection circuit 300. In detail, the processor 123 may set thecandidate quantity of electric charge by increasing, by a certainamount, the current amount of the current source Idc and the operationtime of the switch SW.

In operation 540, the processor 123 determines whether the amount of thefirst component from which the candidate quantity of electric charge isremoved is less than the amount of the offset. For example, when thefirst component is a voltage corresponding to the ridge of afingerprint, the processor 123 determines whether the amount of thevoltage corresponding to the ridge of a fingerprint from which thecandidate quantity of electric charge is removed is less than the amountof the offset. When the amount of the first component from which thecandidate quantity of electric charge is removed is less than the amountof the offset, the process proceeds to operation 550; otherwise, theprocess goes to operation 530, thereby resetting the candidate quantityof electric charge.

In operation 550, the processor 123 determines a final quantity ofelectric charge. The processor 123 may determine the final quantity ofelectric charge such that the amount of the first component from whichthe quantity of electric charge is removed is not less than the offset.For example, the processor 123 may determine a candidate quantity ofelectric charge before the amount of the first component from which thecandidate quantity of electric charge is removed is less than theoffset, to be the final quantity of electric charge.

While the processor 123 repeatedly performs operations 530 and 540 untilthe amount of the first component from which the quantity of electriccharge is removed is not less than the offset, the processor 123 maystore each of the candidate quantities of electric charge in the memory124 and assign a reference number to each of the candidate quantities ofelectric charge in the order in which the candidate quantities ofelectrical charge are applied in operation 530. The reference number mayindicate the number of times that each of operations 530 and 540 isperformed. When the processor 123 determines that the condition ofoperation 540 is satisfied at the n^(th) operation of operation 540, theprocessor 123 may retrieve the candidate quantity of electric chargethat is set at the n−1^(th) operation of operation 530, based on thereference number n−1^(th) associated with the n−1^(th) operation ofoperation 530. For example, the processor 127 may control the memory 124to store the following data:

Reference Candidate quantity of electric Whether condition of No. chargeset in operation 530 operation 540 is satisfied 1 5 No. 2 10 No. 3 20No. 4 30 No. 5 40 Yes.

An example in which the processor 123 determines a final quantity ofelectric charge is described below in detail with reference to FIG. 6.

FIG. 6 illustrates an example of determining, by a processor, a finalquantity of electric charge according to an example embodiment.

First, the processor 123 determines the output value of the ADC of thedetection circuit 300 to be an offset 610. Then, the processor 123checks a first component 620 from the electrical quantity input to thedetection circuit 300.

The processor 123 sets the candidate quantity of electric charge byadjusting the current amount of the current source Idc of the detectioncircuit 300 and the operation time of the switch SW. For example, theprocessor 123 may increase the amount of the candidate quantity ofelectric charge by increasing the current amount and the operation timeby a certain amount.

The processor 123 checks whether the results 631, 632, and 633 obtainedby removing the candidate quantity of electric charge from the firstcomponent 620 is less than the offset 610. The processor 123 performsthe process of setting the candidate quantity of electric charge, mtimes, where m is a natural number, and checks whether the results 631,632, and 633 obtained by removing the candidate quantity of electriccharge from the first component 620 is less than the offset 610.

For example, when the result 631 of removing a first candidate quantityof electric charge from the first component 620 is greater than theoffset 610, the processor 123 sets a second candidate quantity ofelectric charge and repeats the above-described process. In such amanner, when the result 633 of removing the (n+1)th, where n is anatural number, candidate quantity of electric charge from the firstcomponent 620 is, for the first time, less than the offset 610, theprocessor 123 determines the n-th candidate quantity of electric chargeto be the final quantity of electric charge. In other words, when theresult 632 of removing the n-th candidate quantity of electric chargefrom the first component 620 most closely exceeds the offset 610, theprocessor 123 determines the n-th candidate quantity of electric chargeto be the final quantity of electric charge.

The candidate quantity of electric charge may be set as the currentamount of the current source Idc of the detection circuit 300 and theoperation time of the switch SW are adjusted. For example, the processor123 may set the candidate quantity of electric charge by performing atwo-step adjustment process.

As an example, the processor 123 may perform a first step adjustmentprocess to determine the maximum operation time of the switch SW byincreasing the operation time of the switch SW when the current amountof the current source Idc is fixed. The processor 123 may perform thesecond step adjustment process to determine the maximum current amountof the current source Idc by adjusting the current amount of the currentsource Idc and the operation time of the switch SW altogether.

As another example, the processor 123 may perform the first stepadjustment process to determine the maximum current amount of thecurrent source Idc by increasing the current amount of the currentsource Idc when the operation time of the switch SW is fixed. Theprocessor 123 may perform the second step adjustment process todetermine the maximum operation time of the switch SW by adjusting thecurrent amount of the current source Idc and the operation time of theswitch SW altogether.

An example in which a processor sets the candidate quantity of electriccharge by performing the two-step adjustment processes is describedbelow in detail with reference to FIGS. 7, 8, and 9.

FIG. 7 is a flowchart of an example of setting, by a processor 1123, acandidate quantity of electric charge according to an exampleembodiment.

Referring to FIG. 7, the first step adjustment process may includeoperations 710 to 740. Furthermore, the second step adjustment processmay include operations 750 to 770.

In operation 710, the processor 123 fixes the amount of a currentsupplied from the current source Idc to a specific value. For example,the specific value may be a default value of the apparatus 100, and maybe adaptively changed according to the object detected by the sensor 110or the number of integrals. Furthermore, the specific value may bechanged by a user.

In operation 720, the processor 123 increases the operation time of theswitch SW. In other words, the processor 123 increases the time duringwhich the switch SW is closed and becomes a conductive state.

In operation 730, the processor 123 determines whether the amount of thefirst component from which the first candidate quantity of electriccharge is removed is less than the amount of the offset. For example,the processor 123 may calculate the first candidate quantity of electriccharge by multiplying the amount of the current supplied from thecurrent source Idc and the operation time of the switch SW. When theamount of the first component from which the first candidate quantity ofelectric charge is removed is greater than the amount of the offset, theprocess goes to operation 720; otherwise, the process goes to operation740.

In operation 740, the processor 123 determines the maximum operationtime of the switch SW. For example, the processor 123 selects thecandidate quantity of electric charge before the amount of the firstcomponent from which the first candidate quantity of electric charge isremoved is, for the first time, less than the offset. The processor 123determines the operation time used for calculating the selectedcandidate quantity of electric charge to be the maximum operation time.The process of selecting, by the processor 123, the candidate quantityof electric charge is described above with reference to FIGS. 5 and 6.

In summary, in operation 710, the amount of the current supplied fromthe current source Idc is determined, and in operation 740, theoperation time of the switch SW is determined. However, the amount ofthe current and the operation time which are determined as operations710 to 740 are performed may not be optimal results. This is because, inoperation 710, it is assumed that the amount of the current is fixed toa specific value. Accordingly, the processor 123 may determine anoptimal amount of the current and an optimal operation time byperforming a coarse adjustment through the first step adjustment processand a fine adjustment through the second step adjustment process.

In operation 750, the processor 123 adjusts the operation time of theswitch SW and the amount of the current supplied from the current sourceIdc. In operation 760, the processor 123 determines whether the amountof the first component from which the second candidate quantity ofelectric charge is removed is less than the amount of the offset. Forexample, the processor 123 may calculate the second candidate quantityof electric charge by multiplying the amount of a current and theoperation time which are adjusted in operation 750. When the amount ofthe first component from which the first candidate quantity of electriccharge is removed is greater than the amount of the offset, the processgoes to operation 750; otherwise, the process goes to operation 770.

In operation 770, the processor 123 determines the maximum currentamount of the current source Idc. For example, the processor 123 selectsthe candidate quantity of electric charge before the amount of the firstcomponent from which the second candidate quantity of electric charge isremoved is, for the first time, less than the offset. The processor 123determines the current amount used to calculate the selected candidatequantity of electric charge to be the maximum current amount. Theprocess of selecting, by the processor 123, the candidate quantity ofelectric charge is described above with reference to FIGS. 5 and 6.

FIG. 8 illustrates in detail the method described in the flowchart ofFIG. 7 according to an example embodiment.

FIG. 8 illustrates an example of a table consisting of the currentamount I of the current source Idc, the operation time T of the switchSW, and, the electric charge quantity Q. The electric charge quantity Qis calculated by multiplying the current amount I and the operation timeT.

It is assume that the operation time T may be changed by one from 1 to20 and that the current amount I may be changed by one from 1 to 20.Furthermore, a range from 1 to 20 is assumed to indicate a relativeamount from the minimum value to the maximum value of each of theoperation time T and the current amount I. In this case, the totalnumber of combinations of [the operation time T, the current amount I]to be selected by the processor 123 is 400. Accordingly, a lot ofcalculations may be necessary to determine the optimal operation time Tand the optimal current amount I. As the processor 123 performs thefirst step adjustment and the second step adjustment, the amount ofcalculations needed for determining the optimal operation time T and theoptimal current amount I may be reduced.

The processor 123 may perform the first step adjustment by increasingone of the current amount I and the operation time T while fixing theother to a specific value. For example, the processor 123 may performthe first step adjustment in which the amount of the operation time T isincreased while the current amount I is fixed to 14. For example, FIG. 8illustrates that the maximum operation time T is determined to be 12according to the first step adjustment.

In FIG. 8, as the current amount I is assumed to be fixed to 14 in thefirst step adjustment, the electric charge quantity Q of 6.72 C, whichis a result of the first step adjustment, may not be an optimal quantityof electric charge. In other words, the optimal electric charge quantityQ may be any value in a range of 6.72 C to 7.28 C, and thus the optimalelectric charge quantity Q may not be fixed to 6.72 C.

The processor 123 may perform the second step adjustment by adjustingthe current amount I and the operation time T. In FIG. 8, as the secondstep adjustment is performed, it may be checked that the optimalelectric charge quantity Q is 7.2 C, and thus the maximum operation timeT may be determined to be 12 and the maximum current amount I may bedetermined to be 15.

According to the above description with reference to FIGS. 7 and 8, theprocessor 123 may perform the first step adjustment while fixing thecurrent amount I supplied from the current source Idc, but thedisclosure is not limited thereto.

An example of performing, by the processor 123, the first stepadjustment while fixing the operation time T of the switch SW isdescribed below with reference to FIG. 9.

FIG. 9 is a flowchart of another example of setting, by a processor, acandidate quantity of electric charge according to an exampleembodiment.

Referring to FIG. 9, the first step adjustment process may includeoperations 910 to 940. Furthermore, the second step adjustment processmay include operations 950 to 970.

In operation 910, the processor 123 fixes the operation time of theswitch SW to a specific value. For example, the specific value may be adefault value of the apparatus 100, or may be adaptively changedaccording to the object detected by the sensor 110 or the number ofintegrals. Furthermore, the specific value may be changed by a user.

In operation 920, the processor 123 increases the current amount of thecurrent source Idc. In operation 930, the processor 123 determineswhether the amount of the first component from which the third candidatequantity of electric charge is removed is less than the amount of theoffset. When the amount of the first component from which the thirdcandidate quantity of electric charge is removed is greater than theamount of the offset, the process goes to operation 920; otherwise, theprocess goes to operation 940.

In operation 940, the processor 123 determines the maximum currentamount of the current source Idc. For example, the processor 123 selectsthe candidate quantity of electric charge before the amount of the firstcomponent from which the first candidate quantity of electric charge isremoved is, for the first time, less than the offset. The processor 123determines the current amount used to calculate the selected candidatequantity of electric charge to be the maximum current amount. Theprocess of selecting, by the processor 123, the candidate quantity ofelectric charge is described above with reference to FIGS. 5 and 6.

In operation 950, the processor 123 adjusts the operation time of theswitch SW and the amount of the current supplied from the current sourceIdc. In operation 960, the processor 123 determines whether the amountof the first component from which the fourth candidate quantity ofelectric charge is removed is less than the amount of the offset. Whenthe amount of the first component from which the fourth candidatequantity of electric charge is removed is greater than the amount of theoffset, the process goes to operation 950; otherwise, the process goesto operation 970.

In operation 970, the processor 123 determines the maximum operationtime of the switch SW. For example, the processor 123 selects acandidate quantity of electric charge before the amount of the firstcomponent from which the second candidate quantity of electric charge isremoved is, for the first time, less than the offset. The processor 123determines the operation time used to calculate the selected candidatequantity of electric charge to be the maximum operation time. Theprocess of selecting, by the processor 123, the candidate quantity ofelectric charge is described above with reference to FIGS. 5 and 6.

FIG. 10 illustrates another example of a detection circuit 1000 includedin a receiving circuit according to an example embodiment.

FIG. 10 illustrates an example of the detection circuit 1000. When thedetection circuit 300 of FIG. 3 and the detection circuit 1000 of FIG.10 are compared with each other, the first part 310 may correspond to afirst part 1010, and the second part 320 may correspond to a second part1020. The first part 1010 may further include an ADC.

The detection circuit 1000 may include a third part 1030, and the thirdpart 1030 may control the operation time of a switch and the currentamount of a current source, which are included in the second part 1020.Although FIG. 10 illustrates that the third part 1030 includes aseparate processor 1033, and that the processor 1033 controls theoperation time of a switch and the current amount of a current source,the disclosure is not limited thereto. When the processor 1033 isomitted in the third part 1030, the above-described functions of theprocessor 1033 may be performed by the processor 123.

The third part 1030 may include a first register 1031 corresponding tothe switch and a second register 1032 corresponding to the currentsource. Referring to FIGS. 3 to 9, the setting of the operation time ofthe switch may be stored in the register 1031, and the setting of thecurrent amount of the current source may be stored in the secondregister 1032. Furthermore, the first register 1031 and the secondregister 1032 each may be included, as a single configuration, in thethird part 1030.

According to the above description, the apparatus 100 may determine theoptimal quantity of electric charge for each detection circuit, and setthe current amount of the current source and the operation time of theswitch according to the determined quantity of electric charge.Accordingly, without a limitation of an integral limit value, theapparatus 100 may perform a sufficient number of integrals with respectto a valid quantity of electric charge needed for generating an image.Accordingly, the apparatus 100 may generate a high quality image of anobject detected by the sensor.

FIG. 11 illustrates a fingerprint image according to an exampleembodiment and fingerprint images according to comparative examples.

According to an example embodiment, a quantity of electric charge whichis to be removed from each of the plurality of detection circuits 300,is optimized for each of a plurality of detection circuits 300 accordingto an amplifier characteristic (e.g., an input amplifier offset voltage)of each of the plurality of detection circuits 300.

According to comparative example 1, electric charge is not removed fromthe plurality of detection circuits 300. According to comparativeexample 2, the same amount of electric charge is removed from each ofthe plurality of detection circuits 300, without an optimizationprocess.

With reference to the graph of the example embodiment indicating therelationship between the number of integrations and output voltagesV_(OUT1)-V_(OUT4) that are respectively output from the plurality ofdetection circuits 300, it is capable to perform a greater number ofintegrations than comparative examples 1 and 2. Therefore, a higherquality of a fingerprint image may be generated according to the exampleembodiment than comparative examples 1 and 2.

Also, as shown in FIG. 11, a fingerprint image A that is generated anddisplayed on the display 125 of the apparatus 100 according to theexample embodiment, has a higher resolution than fingerprint images Band C generated and displayed according to comparative examples 1 and 2.

The above-described method can be written as computer programs and canbe implemented in general-use digital computers that execute theprograms using a computer-readable recording medium. Furthermore, thestructure of data used in the above-described method may be recorded ona computer-readable recording medium through various means. Examples ofthe computer-readable recording medium include magnetic storage media(e.g., ROM, floppy disks, hard disks, etc.), optical recording media(e.g., CD-ROMs, or DVDs), etc.

It should be understood that example embodiments described herein shouldbe considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment should typically be considered as available for other similarfeatures or aspects in other example embodiments. While one or moreexample embodiments have been described with reference to the figures,it will be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope as defined by the following claims.

What is claimed is:
 1. A method of generating a fingerprint image, themethod comprising: determining a quantity of electric charge to beremoved from each of a plurality of detection circuits connected to afingerprint sensor, based on an amplifier characteristic of each of theplurality of detection circuits; obtaining a second electrical quantityby removing the quantity of electric charge from a first electricalquantity that is input to each of the plurality of detection circuits;integrating the second electrical quantity to obtain an integratedvalue; and generating the fingerprint image based on comparison betweenthe integrated value of the second electrical quantity and apredetermined threshold value.
 2. The method of claim 1, wherein each ofthe plurality of detection circuits comprises a current source, and aswitch configured to connect the current source to the plurality ofdetection circuits according to a control signal, and wherein thedetermining the quantity of electric charge comprises determining thequantity of electric charge based on an amount of a current generatedfrom the current source included in each of the plurality of detectioncircuits and a turn-on time of the switch.
 3. The method of claim 1,wherein the predetermined threshold value corresponds to an input offsetvoltage of an amplifier included in each of the plurality of detectioncircuits.
 4. The method of claim 3, further comprising determining theinput offset voltage of the amplifier determined based on an outputvalue of an analog-digital converter (ADC) included in each of theplurality of detection circuits.
 5. The method of claim 3, wherein thedetermining the quantity of electric charge comprises determining thequantity of electric charge such that a first component of the firstelectrical quantity is not less than the input offset voltage of theamplifier.
 6. The method of claim 2, further comprising: determining amaximum turn-on time of the switch during which a first component of thefirst electrical quantity is not less than an input offset voltage of anamplifier included in each of the plurality of detection circuits, byincreasing the turn-on time of the switch while the amount of thecurrent generated from the current source is fixed; and determining amaximum current amount of the current source at which the firstcomponent is not less than the input offset voltage of the amplifier, byadjusting the turn-on time of the switch and the amount of the currentgenerated from the current source, wherein the obtaining the secondelectrical quantity comprises obtaining the second electrical quantityby determining the quantity of electric charge based on the maximumturn-on time and the maximum current amount, and by removing thedetermined quantity of electric charge from the first electricalquantity.
 7. The method of claim 2, further comprising: determining amaximum current amount of the current source at which a first componentof the first electrical quantity is not less than an input offsetvoltage of an amplifier included in each of the plurality of detectioncircuits, by increasing the amount of the current generated from thecurrent source, when the turn-on time of the switch is fixed; anddetermining a maximum turn-on time of the switch during which the firstcomponent is not less than the input offset voltage, by adjusting theturn-on time of the switch and the amount of the current generated fromthe current source, wherein the obtaining the second electrical quantitycomprises obtaining the second electrical quantity by determining thequantity of electric charge based on the maximum current amount and themaximum turn-on time, and by removing the quantity of electric chargefrom the first electrical quantity.
 8. The method of claim 1, furthercomprising, based on the integrated value being greater than or equal tothe predetermined threshold value, repeating at least once thedetermining the quantity of electric charge and the integrating thesecond electrical quantity.
 9. The method of claim 1, wherein thepredetermined threshold value represents a signal-to-noise ratio of eachof the plurality of detection circuits.
 10. A non-transitorycomputer-readable recording medium having recorded thereon a program forexecuting the method of claim
 1. 11. An apparatus comprising: afingerprint sensor comprising a plurality of drive electrodes and aplurality of detection electrodes; a plurality of detection circuitsconnected to the fingerprint sensor; and at least one processorconfigured to: determine a quantity of electric charge to be removedfrom each of the plurality of detection circuits, based on an amplifiercharacteristic of each of the plurality of detection circuits; obtain asecond electrical quantity by removing the quantity of electric chargefrom a first electrical quantity that is input to each of the pluralityof detection circuits; integrate the second electrical quantity toobtain an integrated value; and generate a fingerprint image based oncomparison between the integrated value of the second electricalquantity and a predetermined threshold value.
 12. The apparatus of claim11, wherein each of the plurality of detection circuits comprises acurrent source, and a switch configured to connect the current source tothe plurality of detection circuits according to a control signal, andwherein the at least one processor is further configured to determinethe quantity of electric charge based on an amount of a currentgenerated from the current source included in each of the plurality ofdetection circuits and an turn-on time of the switch.
 13. The apparatusof claim 11, wherein each of the plurality of detection circuitscomprises an amplifier, and wherein the predetermined threshold valuecorresponds to an input offset voltage of the amplifier included in eachof the plurality of detection circuits.
 14. The apparatus of claim 13,wherein the at least one processor is further configured to determinethe input offset voltage of the amplifier based on an output value of ananalog-digital converter (ADC) included in each of the plurality ofdetection circuits.
 15. The apparatus of claim 13, wherein the at leastone processor is further configured to determine the quantity ofelectric charge such that a first component of the first electricalquantity is not less than the input offset voltage of the amplifier. 16.The apparatus of claim 12, wherein the at least one processor is furtherconfigured to: determine a maximum turn-on time during which a firstcomponent of the first electrical quantity is not less than an inputoffset voltage of an amplifier included in each of the plurality ofdetection circuits, by increasing the turn-on time of the switch whilethe amount of the current generated from the current source is fixed;determine a maximum current amount of the current source at which thefirst component is not less than the input offset voltage of theamplifier, by adjusting the turn-on time and the amount of the currentgenerated from the current source; and obtain the second electricalquantity by determining the quantity of electric charge based on themaximum turn-on time and the maximum current amount and by removing thedetermined quantity of electric charge from the first electricalquantity.
 17. The apparatus of claim 12, wherein the at least oneprocessor is further configured to: determine a maximum current amountof the current source at which a first component of the first electricalquantity is not less than an input offset voltage of an amplifierincluded in each of the plurality of detection circuits, by increasingthe amount of the current generated from the current source, when theturn-on time of the switch is fixed; determine a maximum turn-on time ofthe switch during which the first component is not less than the inputoffset voltage, by adjusting the turn-on time of the switch and theamount of the current generated from the current source, and obtain thesecond electrical quantity by determining the quantity of electriccharge based on the maximum current amount and the maximum turn-on time,and by removing the quantity of electric charge from the firstelectrical quantity.
 18. The apparatus of claim 11, wherein the at leastone processor is further configured to, based on the integrated valuebeing greater than or equal to the predetermined threshold value, repeatat least once an operation of determining the quantity of electriccharge and an operation of integrating the second electrical quantity.19. The apparatus of claim 11, wherein the predetermined threshold valuerepresents a signal-to-noise ratio of each of the plurality of detectioncircuits.
 20. An electronic apparatus comprising: a fingerprint sensorcomprising a plurality of drive electrodes and a plurality of detectionelectrodes; a plurality of detection circuits configured to receive afirst electrical quantity from the plurality of detection electrodes ofthe fingerprint sensor, respectively, the plurality of detectioncircuits comprising an analog-digital converter (ADC), a current source,and a switch configured to connect the current source to the ADC; and atleast one processor configured to: determine a candidate quantity ofelectric charge to be removed from each of the plurality of detectioncircuits, based on an output voltage of the ADC; integrate a secondelectrical quantity that is obtained by removing the candidate quantityof electric charge from the first electrical quantity, a first number oftimes until the first electrical quantity becomes less than apredetermined threshold value; and determine a final quantity ofelectric charge to be removed from each of the plurality of detectioncircuits, based on an integrated value of the second electrical quantitythat is obtained by integrating the second electrical quantity a secondnumber time that is one less than the first number of times; andgenerate a fingerprint image by removing the final quantity of electriccharge from the plurality of detection circuits.